Grain boundary diffusion process using soaking rolling mode

Abstract

The invention discloses a grain boundary diffusion process using a soaking rolling mode, which comprises the following steps: polishing the surface of a neodymium iron boron product to be smooth, heating to remove oil, drying with hot air to obtain a to-be-permeated pretreated product, completely immersing the pretreated product into slurry for soaking, taking out a tool, standing, and draining off redundant slurry on the surface, thereby obtaining the neodymium iron boron product. Transferring the product into a baking furnace, slowly forming a coating film on the surface of the pretreated product, and putting the coated product into a vacuum sintering furnace for heat treatment and heat preservation to obtain a permeated product; and polishing the permeated product, and testing the magnetic performance parameters of the permeated product. The invention relates to the technical field of magnet materials. According to the grain boundary diffusion process using the soaking and rolling mode, a uniform coating film is formed on the surface of a product by adopting a mode of soaking and then rolling attachment, the problem that the coating process cannot control the consistency of a coating layer is solved, and the material consumption of heavy rare earth is reduced, so that the production cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of magnet materials, in particular to a grain boundary diffusion process using an immersion rolling method. Background Art

[0002] In recent years, with the popularization and application of sintered NdFeB in various fields, especially in the fields of electric vehicles and small electronic products, higher requirements have been put forward for the maximum magnetic energy product, coercive force, high temperature resistance and production cost of NdFeB, so grain boundary diffusion technology has become very popular. Grain boundary diffusion technology uses heavy rare earth to attach a layer of heavy rare earth film on the surface of magnetic steel, and then heats it in high temperature vacuum to make heavy rare earth atoms replace neodymium atoms to form a high coercive force shell. In this way, a high coercive force and high temperature resistant NdFeB product can be obtained using a small amount of heavy rare earth.

[0003] In the prior art, the grain boundary diffusion processes mainly include magnetron sputtering, screen printing, surface spraying, electrophoretic deposition and other methods. Among them, the screen printing process has been widely used in recent years due to its high production efficiency. However, the prior art has the following problems: it can only print the flat surface of the product, and there is a problem of not being able to evenly coat the product with curved surfaces. In addition, due to the limitations of the printing process, for products with different requirements for heavy rare earth weight gain, corresponding stencils and tooling need to be customized, and the interchangeability is poor. When producing products with a large variety and a fast iteration speed, the production cost is high and the delivery cycle is long. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a grain boundary diffusion process using an immersion rolling method, which solves the problem that only the flat surface of the product can be printed, and the product with curved surface cannot be coated evenly, as well as the problems of high production cost and long delivery cycle.

[0005] To achieve the above objectives, the present invention is implemented by the following technical solutions: a grain boundary diffusion process using an immersion rolling method, the specific process includes the following steps:

[0006] Step 1: Grind the surface of the NdFeB product until it is smooth, and then heat it to remove oil and dry it with hot air to obtain a pre-treated product to be infiltrated;

[0007] Step 2: Prepare a slurry using any one of heavy rare earth metal powder, heavy rare earth metal oxide powder or non-metal;

[0008] Step 3: Immerse the pretreated product completely in the slurry, take out the tooling and let it stand for a while, then drain off the excess slurry on the surface. For products with high weight gain requirements, the standing time needs to be shortened to ensure sufficient slurry adhesion;

[0009] Step 4: Place the product in a drying oven, and then roll the drum to slowly form a coating film on the surface of the pretreated product;

[0010] Step 5: Then increase the temperature of the drying oven and adjust the rolling speed to form a uniform and firm coating film on the surface of the product. For products with high weight gain requirements, the rolling time needs to be shortened to ensure the thickness of the coating film;

[0011] Step 6: Pack the coated product with a graphite box, place it in a vacuum sintering furnace for heat treatment and keep it warm, then cool the coated product and temper it, and then keep it warm to obtain the infiltrated product;

[0012] Step 7: Polish the infiltrated product and test the magnetic performance parameters of the infiltrated product. This process simulates the impact of polishing and pickling processes in actual production on the surface penetration layer.

[0013] Preferably, in step three, the product soaking time is 30 seconds, and the standing time is 30 to 120 seconds.

[0014] Preferably, in step 4, the temperature of the drying oven is 60° C., the speed of the drum is 15 r / min, and the time is 30 minutes.

[0015] Preferably, in step 5, the temperature of the drying furnace is increased to 150° C., and the speed of the drum is 30 r / min for 30 to 120 minutes.

[0016] Preferably, in step six, the temperature of the vacuum sintering furnace is 800-1000° C. and is kept warm for 8-18 hours, and the cooling temperature is 80° C. and is kept warm at 480-650° C. for 4-10 hours.

[0017] Preferably, the product polished in step seven is 0.04-0.06 mm.

[0018] The present invention provides a grain boundary diffusion process using an immersion rolling method. Compared with the prior art, it has the following beneficial effects:

[0019] The grain boundary diffusion process using the immersion rolling method forms a uniform coating film on the product surface by immersing and then rolling. This solves the problem that the coating process cannot control the consistency of the coating layer, reduces the use of heavy rare earth materials, and thus significantly reduces production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the present invention; DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] See also Figure 1 The embodiment of the present invention provides a technical solution: a grain boundary diffusion process using an immersion rolling method, the specific process includes the following steps:

[0023] Step 1: Grind the surface of the NdFeB product until it is smooth, and then heat it to remove oil and dry it with hot air to obtain a pre-treated product to be infiltrated;

[0024] Step 2: Prepare a slurry using heavy rare earth metal powder or heavy rare earth metal oxide powder or other non-metallic components;

[0025] Step 3: Immerse the pretreated product completely in the slurry. After soaking for 30 seconds, take out the tooling and let it stand for 30 to 120 seconds to drain the excess slurry on the surface. For products with high weight gain requirements, the standing time needs to be shortened to ensure sufficient slurry adhesion;

[0026] Step 4: Place the product in a drying oven at 60°C and roll it in a drum at a speed of 15r / min for 30 minutes to slowly form a coating film on the surface of the pretreated product;

[0027] Step 5: Raise the temperature of the oven to 150°C, and then adjust the rolling speed to 30r / min for 30 to 120 minutes to form a uniform and firm coating film on the surface of the product. For products with high weight gain requirements, the rolling time needs to be shortened to ensure the thickness of the coating film.

[0028] Step 6: Pack the coated product with a graphite box, place it in a vacuum sintering furnace for heat treatment, keep it at 800-1000°C for 8-18 hours, cool the coated product to 80°C, then temper it, keep it at 480-650°C for 4-10 hours, and obtain the infiltrated product;

[0029] Step 7: Grind the infiltrated product by 0.04-0.06 mm and test the magnetic performance parameters of the infiltrated product. This process simulates the effects of polishing and pickling procedures on the surface penetration layer in actual production.

[0030] Example

[0031] The surface of the NdFeB product is polished to be smooth, and heated to remove oil and hot air dried to obtain a pre-treated product to be infiltrated. Preferably, the product is 4 cylindrical products of φ10mm*10mm, which are marked as sample 1, sample 2, sample 3, and comparative example 1 by a laser marking machine, and the weight is recorded, wherein comparative example 1 does not undergo the following infiltration process.

[0032] The slurry is made of heavy rare earth metal powder or heavy rare earth metal oxide powder or other non-metallic components. Preferably, the slurry in this embodiment contains dysprosium. Furthermore, the heavy rare earth metals mainly include gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc. The heavy rare earth metal powder is powder made of these heavy rare earth metals.

[0033] Heavy rare earth metal oxide powder is the powder corresponding to the oxides formed by these heavy rare earth metals, such as powders of gadolinium oxide (Gd2O3), terbium oxide (Tb4O7), dysprosium oxide (Dy2O3), etc., as well as non-metallic components such as boron, carbon, oxygen, nitrogen, hydrogen and other elements. In this process, they can be used to make slurry to process NdFeB products and improve product performance.

[0034] The pretreated product was completely immersed in the slurry. After soaking for 30 seconds, the tooling was taken out and allowed to stand for 60 seconds to drain off the excess slurry on the surface. Furthermore, the product gained 0.6% dysprosium.

[0035] Place the tooling into the drum and roll it at a speed of 15r / min for 30 minutes. At the same time, use 40°C hot air to dry the drum so that a coating film is slowly formed on the surface of the pretreated product.

[0036] Take out the tooling, move it to a 120°C drying oven, and roll it at a speed of 30 r / min for 30 minutes to form a uniform and firm coating film on the surface of the product, and record the weight at this time.

[0037] The coated product is packed in a graphite box and placed in a vacuum sintering furnace for heat treatment at 800-1000°C for 8-18 hours. The coated product is cooled to 80°C and then tempered, and then heated to 480-650°C and kept for 4-10 hours to obtain an infiltrated product.

[0038] The infiltrated product was polished by 0.04-0.06 mm to simulate the influence of the centerless grinding and pickling process in actual production on the surface penetration layer. The magnetic performance parameters of the infiltrated product were tested to obtain Example 1.

[0039] Table 1: Parameter comparison of Example 1

[0040]

[0041] The experimental data analysis shows that the weight gain difference of dysprosium in this embodiment is 0.001 g, and the weight gain ratio difference is 0.0017%. The weight gain difference is small, the coating layer is uniform, and the remanence consistency is high.

[0042] Therefore, the problem that the coating process cannot control the consistency of the coating layer is solved, the use of heavy rare earth materials is reduced, and the production cost is greatly reduced.

[0043] This process is not limited by the shape of the product, and can efficiently produce NdFeB products with different shapes and difficult special-shaped surfaces. In addition, this process has great advantages in responding to the market's demand for rapid iteration of NdFeB products, and can develop new products quickly and efficiently, and quickly seize market opportunities. Especially for NdFeB products with a size of less than 25mm×25mm×25mm and with curved surfaces, such as tiles, mason jars, rings, etc., it has great cost advantages.

[0044] It is worth mentioning that this process has obvious advantages when the product requires both high remanence and high coercivity. The coating layer of the product made in this way is uniform. After high-temperature infiltration, the infiltration layer formed by heavy rare earth on the surface of the NdFeB product has good consistency. When the coercivity is increased to the same extent, the remanence is significantly improved.

[0045] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0046] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0047] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A grain boundary diffusion process using an immersion rolling method, characterized in that: The specific process includes the following steps: Step 1: Grind the surface of the NdFeB product until it is smooth, and then heat it to remove oil and dry it with hot air to obtain a pre-treated product to be infiltrated; Step 2: Prepare a slurry using any one of heavy rare earth metal powder, heavy rare earth metal oxide powder or non-metal; Step 3: completely immerse the pre-treated product in the slurry, take out the tooling and let it stand to drain off the excess slurry on the surface; Step 4: Place the product in a drying oven, and then roll the drum to slowly form a coating film on the surface of the pretreated product; Step 5: Then increase the temperature of the drying oven and adjust the rolling speed to form a uniform and firm coating film on the surface of the product; Step 6: Pack the coated product with a graphite box, place it in a vacuum sintering furnace for heat treatment and keep it warm, then cool the coated product and temper it, and then keep it warm to obtain the infiltrated product; Step 7: Polish the infiltrated product and test the magnetic performance parameters of the infiltrated product.

2. The grain boundary diffusion process using an immersion rolling method according to claim 1, characterized in that: In the step 3, the product is immersed for 30 seconds and is left to stand for 30 to 120 seconds.

3. The grain boundary diffusion process using an immersion rolling method according to claim 1, characterized in that: In the step 4, the temperature of the drying oven is 60° C., the speed of the drum is 15 r / min, and the time is 30 minutes.

4. The grain boundary diffusion process using an immersion rolling method according to claim 1, characterized in that: In the step 5, the temperature of the drying furnace is increased to 150° C., the speed of the drum is 30 r / min, and the time is 30 to 120 minutes.

5. The grain boundary diffusion process using an immersion rolling method according to claim 1, characterized in that: In the step six, the temperature of the vacuum sintering furnace is 800-1000° C. and is kept warm for 8-18 hours, and the cooling temperature is 80° C. and is kept warm at 480-650° C. for 4-10 hours.

6. The grain boundary diffusion process using an immersion rolling method according to claim 1, characterized in that: The product polished in step seven has a thickness of 0.04 to 0.06 mm.

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